Andrew is doing some tidying. He can tidy 2 big rooms in the same time it takes to tidy 3 small rooms. He can tidy one big room and three small rooms in 90 minutes. How long will it take him to tidy 3 big rooms and 6 small rooms? - AMC (Australian Mathematical Competition) Upper Primary 2018, Question 20 AMC Upper Primary 2018, Question 20 In this post, we solve AMC (Australian Mathematical Competition) Upper Primary 2018 Question 20 step by step using visual models and simpl

Ryan got 80% of the problems correct on a 25-problem test, 90% on a 40-problem test, and 70% on a 10-problem test.

In a jar of red, green, and blue marbles, all but 6 are red marbles, all but 8 are green, and all but 4 are blue. How many marbles are in...